This is in answer to this Stack Overflow question about how to place points on a map and how projections work.
Last active
September 9, 2018 12:23
-
-
Save phil-pedruco/7745589 to your computer and use it in GitHub Desktop.
Plotting points on a map in D3
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>Point on a map D3</title> | |
| <script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script> | |
| <script src="http://d3js.org/topojson.v1.min.js"></script> | |
| <style type="text/css"> | |
| .feature { | |
| fill: none; | |
| stroke: grey; | |
| stroke-width: 1px; | |
| stroke-linejoin: round; | |
| } | |
| .mesh { | |
| fill: none; | |
| stroke: lightgrey; | |
| stroke-width: 2px; | |
| stroke-linejoin: round; | |
| } | |
| h1 { | |
| font-family: sans-serif; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <h1>Point in the north west part of SF</h1> | |
| <script type="text/javascript"> | |
| var width = 950, | |
| height = 550; | |
| // set projection | |
| var projection = d3.geo.mercator(); | |
| // create path variable | |
| var path = d3.geo.path() | |
| .projection(projection); | |
| d3.json("us.json", function(error, topo) { console.log(topo); | |
| states = topojson.feature(topo, topo.objects.states).features | |
| // set projection parameters | |
| projection | |
| .scale(1000) | |
| .center([-106, 37.5]) | |
| // create svg variable | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| // points | |
| aa = [-122.490402, 37.786453]; | |
| bb = [-122.389809, 37.72728]; | |
| console.log(projection(aa),projection(bb)); | |
| // add states from topojson | |
| svg.selectAll("path") | |
| .data(states).enter() | |
| .append("path") | |
| .attr("class", "feature") | |
| .style("fill", "steelblue") | |
| .attr("d", path); | |
| // put boarder around states | |
| svg.append("path") | |
| .datum(topojson.mesh(topo, topo.objects.states, function(a, b) { return a !== b; })) | |
| .attr("class", "mesh") | |
| .attr("d", path); | |
| // add circles to svg | |
| svg.selectAll("circle") | |
| .data([aa,bb]).enter() | |
| .append("circle") | |
| .attr("cx", function (d) { console.log(projection(d)); return projection(d)[0]; }) | |
| .attr("cy", function (d) { return projection(d)[1]; }) | |
| .attr("r", "8px") | |
| .attr("fill", "red") | |
| }); | |
| </script> | |
| </body> | |
| </html> |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Hi there. I'm just getting started with D3, and I came across this example on bl.ocks.org. It's really helped me quickly understanding plotting. Thanks!